Go Down

Topic: How to set DUE's native USB port from high-speed to low or full speed? (Read 598 times) previous topic - next topic



I have tried to put the native USB port of Arduino DUE acting as a low speed or full speed device. At this point, I'm a bit lost. All I have managed was to increase signals' levels from 400mVpp (as they are for a high speed device) to 3V. And to get an "unrecognized USB device" message or so.

Do you have a suggestion for a starting point in doing this correctly?
I presume that my USB communication problems of spurious detaching and reattaching of the device are somehow related with a low quality USB cable and a noisy environment. And eventually with my program. So, hardware, software... did I missed something...?  :)

Thank you all!


Hi everybody!

I didn't succeeded to change the native USB settings to make it act as a low or full speed device. So, I moved the communications to the programming port and set it at 921600bps. There is something I don't understand: using RealTerm to monitor the ASCII characters sent by DUE, I have observed that RealTerm doesn't interpret them correctly if is set to 8 bits per character.
However, if I set RealTerm to receive 7 bits characters, I see correct data frames.

I changed the speed back to 115200bps at DUE's side. At that speed, RealTerm is acting normally (characters are received correctly at 8bits/character).

In the same time, it appears to me that serialEvent() doesn't manage to work properly above 115200bps. This is the highest speed at which I succeeded to communicate bidirectionally with DUE.
Above this speed, serialEvent() -which I understood that works similarly to a serial communication ISR- is triggered. It enters on every character, I counted. However, Serial.read() returns zeros, as I somehow get the receiving buffer altered.
I tried few different approaches on serialEvent() and all worked (finally) at 115200bps. At superior speeds, they fail.
As far as I think, there is not a problem of RealTerm: I have the same results by communicating with my LabVIEW application.

Can you help me, please, to understand where I'm do it wrong?

Bellow is a fragment of code. In serialEvent() are few commented variants I have tried.
Thank you for any help!

Code: [Select]

// function which links the serialEvent
// serialEvent wouldn't be called without it
void serialEventRun(void) {
  if (Serial.available()) serialEvent();

void serialEvent()
  char ch = Serial.read();
//  Serial.print(ch);
//  if (ch == '*') len = 0; //synchronize header
  if (ch != -1)  // a valid character
      if (ch == '*') len = 0; //synchronize header
      serial_buffer[len] = ch; len++; 
      if ( (ch == '\n' || ch == '\r') && (serial_buffer[0] == '*') ) {serial_data = true;}
      else if ( (ch == '\n' || ch == '\r') && (serial_buffer[0] != '*') ) len = 0;

/*unsigned char i;
  for (i=0; i<len; i++) {
    serial_buffer[ser_count] = Serial.read();
    if (serial_buffer[ser_count]=='\n') serial_data=true;

//  Serial.readBytes(serial_buffer, len);
//  for (i=0; i<=len; i++) if (serial_buffer[i]=='\n') serial_data = true;

  while (Serial.available()) {
    // get the new byte:
    char inChar = (char)Serial.read();
    // add it to the inputString:
    inputString += inChar;
    // if the incoming character is a newline, set a flag
    // so the main loop can do something about it:
    if (inChar == '\n') serial_data = true;

Code: [Select]

void setup(){

  Wire.begin();  // initialise the I2C connection
  definePins();  // define pin modes for digital I/O
  initialize_digout();  // initialize relay outputs
  get_parameters();  // prototype in Flash_Memory.ino. Reads parameters stored in flash

  // native USB. Used for data streaming
//  SerialUSB.begin(0);

  /* PWM channel initialization */
  /* http://forum.arduino.cc/index.php?topic=198906.0 */
  pmc_enable_periph_clk (PWM_INTERFACE_ID) ;  // turn on clocking to PWM unit

  PWMC_ConfigureChannel (PWM, 6, 1, 0, 0) ; // PWM, channel 6, clock = MCLK/2 = 42MHz
  PWMC_SetPeriod (PWM, 6, 4095) ;  // PWM, channel 6, period = 4095 pwm clocks => 10.256kHz
  //  PWMC_SetDutyCycle (PWM, 6, 200) ;  // PWM, channel 6, duty set
  PWMC_EnableChannel (PWM, 6) ;   // PWM, channel 6 enable

  // Configure pin 7 (PC23) to be driven by peripheral B (PWM channel 6 L)
  // see documentation on SAM microcontroller
  PIOC->PIO_PDR = 1<<23 ;  // disable PIO control
  PIOC->PIO_IDR = 1<<23 ;   // disable PIO interrupts
  PIOC->PIO_ABSR |= 1<<23 ;  // switch to B peripheral

  // Interrupt Service Routine for IGBT_FAULT
  //  attachInterrupt(IGBT_FAULT, igbt_fault, LOW);
  // Interrupt Service Routine for optic sensor
  //  attachInterrupt(50, speed_interrupt, FALLING);
  // se asigneaza rutinei ISR "speed_interrupt()" o intrerupere pe front cazator pe pinul 50
  // speed_interrupt este definita in Freq_Phase_Handlers

  startTimer(); // programarea si pornirea timerelor.

  initialize_PID();  // prototype in PID.ino

void loop()

  //  delay(streamtime);
  if (data_ready == true) {data_ready = false; transmit_values();} // call USB data streaming routine
  if (serial_data == true) {serial_data = false; take_USB_data();}
  if (digitalRead(IGBT_FAULT) == LOW) {delayMicroseconds(20); if (digitalRead(IGBT_FAULT) == LOW) igbt_fault();}

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131